[sailorjoe]

One thing that hasn't been mentioned. On Windows 7, when you change your network adapter settings, you select the entry for IPv4, and select Properties. Then you put in the DS IP address and subnet mask. After that, click Advanced, and check the list off IP addresses. Make sure that the only one showing is the one you input. If there are any others, delete them. This fixed our problem which had similar symptoms.
Good Luck!